Motion detecting mechanisms have been widely used in various fields including home care, motion training for athletes, video games, cinema, etc. A number of conventional motion detecting techniques exist for detecting motion of an object (e.g., a human being). For example, a video of an object may be captured, and image identification operations may be performed to determine motion of the object. Another example is to use a motion sensor unit that includes an accelerometer and an angular acceleration sensor and that can be mounted on or worn by the object, and to use the reading of the motion sensor unit (e.g., gravitational acceleration and angular acceleration) to determine the motion of the object. In general, the motion sensor unit may be included in a mobile device (e.g., a smartphone) or a wearable device.
However, in order to obtain more accurate results, all components of the motion sensor unit are always powered on, thereby potentially draining the power of the mobile device or the wearable device.